I have always despised them for putting a paywall in front of the SQL standard - it's been there since at least 2010 and probably quite a bit earlier. The good news is that nobody actually needs to read it since you need DB specific information anyways... but it'd be nice to have access to it (especially when I was working on RDBMS neutral dialect to support multiple backends). Still, if you ever have a question about documentation postgres[1] does an absolutely amazing job detailing everything in its dialect and their dialect tends to be the most "neutral" imo.

1. https://www.postgresql.org/docs/current/index.html